In the present context the concept of "sorptive capacity" aims at the rate by which the absorbent material takes up liquids such as water or aqueous solutions, including body fluids such as urine, blood and menstrual fluids, or to the liquid-retaining capacity of the absorbent material, or to both of these characteristics. The sorptive mechanism may be adsorption or absorption, or a combination thereof.
As stated in Pulp and Paper Manufacture, Vol. 2, page 280-281, Joint Textbook Committee of the Paper Industry, 1987, hereby incorporated by reference, the term fluff applies to fibres which have been separated by mechanical means from dry pulps for application in dry-formed nonwoven webs or pads in the household or sanitary fields. As is evident from this reference both the rate of liquid uptake and liquid-holding capacity of fluff are important when used in these fields. This is particularly valid with regard to absorbent articles such as catamenial devices (e.g. sanitary napkins, pantiliners, tampons etc.), diapers, bandages, adult incontinence garments, and the like; good liquid uptake and liquid-holding capacity are obvious prerequisites for the function of such articles. However, when used, an article of this kind is constantly subjected to pressure imposed by the weight and the movements of the bearer, and thus it is important that the liquid-holding capacity is high enough to retain the absorbed liquid also under pressure. Furthermore, in order to give good comfort to the bearer, the article should provide a feeling of dryness, meaning that any rewetting from the article to the skin of the bearer should by avoided, raising the requirements with regard to liquid-holding capacity even higher. Conventionally, certain polymeric materials forming hydrogels in contact with water, known as "superabsorbents", have been utilised to enhance the sorptive capacity of such articles; however, although this capacity of the article is enhanced, as the liquid is bound to superabsorbent particles, the sorptive capacity of the cellulosic fibres making up the fluff itself is not in fact enhanced by the use of such superabsorbents.
The problem to be solved by the present invention is thus to provide a method for production of fluff having improved sorptive capacity.
That problem is solved by the method defined by the appended claims.
The reason why hydrophobic substances of the stated kind impose improved sorption characteristics has so far not been clearly established.